The present invention relates to a film deposition apparatus that performs film deposition over a substrate, and to a method of manufacturing a semiconductor device.
The chemical vapor deposition (CVD) process is known as one film deposition technique of the techniques and processes used in the manufacturing process of semiconductor devices. With recent advancement in technology for miniaturization of semiconductor devices, such a film deposition technique is required to be capable of, for example, performing film deposition at low temperature and depositing thin films of high quality.
An atomic layer deposition (ALD) process has the features that film deposition can be implemented at low temperature and film deposition excellent in step-portion coating capability can be accomplished. In the ALD process, two or more different types of reactant gases to be used as source materials of a deposition target film are alternately supplied to a wafer substrate. The gases are adsorbed onto the surface of the substrate by one atomic layer or by one molecular layer, whereby film deposition is performed utilizing chemical reaction on the surface of the substrate.
FIG. 1 is a transverse cross sectional view showing the configuration of a conventional film deposition apparatus that performs film deposition by using the ALD process. The apparatus will be described with reference to an example case where a silicon nitride film is deposited.
In a reactor tube 100, a plurality of wafers 102 are arranged in a vertical direction at a predetermined pitch with the wafer surfaces directed in a horizontal direction.
A buffer chamber 104 is provided to an inner wall of the reactor tube 100. A nozzle 106 for supplying an ammonia gas, and a pair of electrodes 108 for generating plasma are disposed in the buffer chamber 104. The pair of electrodes 108, are respectively equipped in electrode protection tubes 110. The ammonia gas is activated by plasma generated by the pair of electrodes 108 in the buffer chamber 104, and is supplied to the wafers 102 through a gas supply opening 104a of the buffer chamber 104.
Separate from the buffer chamber 104, a gas supply section 112 for supplying a dichlorosilane (DCS) gas is provided. The DCS gas is supplied to the wafers 102 through a gas supply opening 112a in the gas supply section 112.
In film deposition, the activated ammonia gas from the buffer chamber 104 and supply of the DCS gas from the gas supply section 112 are alternately supplied, and the silicon nitride film is formed over the wafers 102.
In the conventional film deposition apparatus, quartz is used as a material for members, such as the buffer chamber, electrode protection tubes, nozzle, gas supply section, in the reactor tube, and for the reactor tube itself. Sodium and the like are contained as impurities in the members comprising quartz. When, during film deposition over the wafers, the plasma is generated in the reactor tube 100, the sodium and the like contained in the quartz member(s) are discharged and, as a consequence, are adsorbed into the film being deposited. When such sodium and the like thus discharged is included in a semiconductor device, deterioration of device properties results.
Generally, in a film deposition apparatus such as described above, an inner wall surface of a reactor receptacle and component members provided in the interior of the reactor receptacle are coated with a film deposited by the CVD process before film deposition over the wafers. The film coating is thus applied for the purposes of, for example, inhibition of contamination with impurities contained in the quartz members, inhibition of particle occurrence, and improvement of film deposition stability.
In a film deposition apparatus employing the ALD process, the inner wall surface of the reactor receptacle and the members in the interior of the reactor receptacle have to be coated with a film deposited by, for example, the CVD or ALD process as a treatment before film deposition over the wafers. In the example case described above, the inner wall surface of the reactor receptacle, the outer surface of the buffer chamber, and the surface of the gas supply section disposed in the exterior of the buffer chamber can be coated with the silicon nitride film.
However, the inner surface of the buffer chamber and the surfaces of the nozzles disposed interiorly of the buffer chamber are difficult to coat with the silicon nitride film. This is because, the reactant gas activated by the plasma discharges from the gas supply opening of the buffer chamber, and this discharge makes it difficult for the other gas, for example, DCS gas which has been supplied from the gas supply section in the exterior of the buffer chamber to flow into the buffer chamber.